The invention relates to mechanisms for sowing seeds, particularly to a single-grain sower, having a container of grains connected to a device which places them into a furrow made by a plowshare.
It is known from British Pat. No. 1,413,849 published Nov. 12, 1975 to provide such a mechanism connected by a coupling rod to a tractor, with wheels before and behind the plowshare connected pivotably by lever arms to the frame that carries the sower. It is important for the depth to which the plowshare enters the ground to be adjustable to suit what is being sowed. For this purpose, that patent discloses the pivotal adjustment of the wheel-carrying lever arms through use of a handwheel with a screw-threaded spindle upon which runs a nut articulated to two links, whose outer ends are coupled to the lever arms. By operating the handwheel, the nut is moved up or down along the screw-threaded spindle, subjecting the lever arms to opposed pivoting movements which changes the location of the axles of the road-wheels, thereby adjusting the penetration of the plowshare into the ground to the desired depth.
This known sower can be coupled to a tractor by a simple linking rod. With some applications, however, it is advantageous to utilize a parallelogram-type coupling of the sower to the tractor, particularly in irregular terrain. However, utilizing such a coupling with a seed sowing mechanism of adjustable depth as disclosed in the British patent produces a mechanism which is unable to follow irregularities in the terrain. It is also important that the front road-wheel presses harder onto the ground than the rear road-wheel so that the front wheel compacts the earth where the seeds are to be sown, while the rear wheel smoothes the furrow. This differing load distribution is also not possible in an arrangement as in the British patent.
The present invention is directed to the coupling of a sower to a tractor by a parallelogram-type coupling while providing for the adjustable depth of the plowshare, and proper following of all irregularities of terrain and the greater loading of front road-wheels than the rear ones.
The invention is characterized in that, particularly with a parallelogram-type coupling, the two wheel-carrying lever arms are connected so that they are able to freely make similar pivoting movements during operation of the sower (i.e., as one wheel moves upwardly, the other wheel moves downwardly) and are not connected rigidly as in the British patent. Both road wheels thus adhere to the ground even where it is irregular, and even though the parallelogram-type coupling provides a firm coupling between the tractor and sower frame. Furthermore, through the use of lever arm appendages of different lengths, e.g., with the front length about double that of the rear, the desired distribution of load between the front and rear wheels (greater in the front) is achieved.
For adjusting the sower to sow to different depths, location of one or both lever arms can be adjusted in height. This adjustment is needed to adapt the sower to different kinds of seeds. The adjustment is preferably done through the location of the rear lever arm being changed by the operation of a crank. Furthermore, the length of the coupling between lever arms may also be variable, so as to additionally adjust the depth of sowing. Still further, by selecting road-wheels of differing sizes, seed sowing depth may also be adjusted.
The invention is explained in more detail in the following detailed description.